Increasing shrinkage risk of endorheic lakes in the middle of farming-pastoral ecotone of Northern China

Lakes are an important water resource and provide a variety of important ecosystem services for humans. Effective monitoring of lake surface area (LSA) dynamics is critical for sustainable management of water re-sources, particularly in arid and semi-arid areas. The interannual and intraannual variations of lakes and their impact factors in the middle of the farming-pastoral ecotone of Northern China (M-FPENC) were analyzed. The results showed that a total of 1192 lakes have appeared during the last 20 years, with a total area of approxi-mately 1145.6 km(2), with most of them having seasonal and ephemeral water. The LSA in the M-FPENC decreased rapidly during 2000-2019. The annual maximum LSA and number of lakes greater than 1 km(2) decreased by 30.04% and 33.00%, respectively. At the intraannual scale, the LSA continued to shrink from April to July, with the lowest value observed in the middle of July, and then gradually recovered. It was found that interannual variations in the lake area mainly depended on the interannual fluctuation in precipitation. The shrinkage of lakes was mainly attributed to the significant increase of land surface evapotranspiration.